One-Punch Man (Japanese: ワンパンマン, Hepburn: Wanpanman) is a Japanese superhero manga series created by One. It tells the story of Saitama, a superhero who, because he can defeat any opponent with a single punch, grows bored from a lack of challenge. One wrote the original webcomic manga version in early 2009.

A digital manga remake, illustrated by Yusuke Murata, began publication on Shueisha's Tonari no Young Jump website in June 2012. Its chapters are periodically compiled and published into individual tankōbon volumes. As of June 2023, 28 volumes have been released. In North America, Viz Media has licensed the remake manga for English language release and has serialized it in its Weekly Shonen Jump digital magazine.

An anime adaptation produced by Madhouse was broadcast in Japan from October to December 2015. A second season, produced by J.C.Staff, was broadcast from April to July 2019. A third season has been announced. Licensed in North America by Viz Media, it premiered in the United States on Adult Swim's Toonami programming block in July 2016. The second season premiered on the block in October 2019.

By June 2012, the original webcomic manga surpassed 7.9 million hits. By April 2020, the manga remake had sold over 30 million copies worldwide, making it one of the best-selling manga series of all time.